Field
The present disclosure relates to diagnostic examinations performed using Magnetic Resonance Imaging (MRI), and more particularly to systems, methods, apparatuses, and computer-readable storage media for performing dental examinations using MRI.
Description of Related Art
Performing diagnostic examinations using conventional MRI systems can be time consuming and complex. Accordingly, highly-skilled technicians can be required to perform such examinations. Before a diagnostic inquiry is performed and a corresponding diagnostic image is recorded in modern clinical practice, a conventional MRI system used to acquire the diagnostic image can require meticulous preparation in order to achieve localization of a target volume and to obtain an optimal image quality, which depends on the particular diagnostic inquiry being performed.
FIG. 8 shows a flow chart 700 of a procedure that can be performed when a conventional MRI system is used to perform a diagnostic examination. The procedure begins in Step S802.
In Step S804, one or more imaging coils are positioned near an area of the patient's body that is to be examined. The imaging coils can be High Frequency (HF) coils, for example, that are integrated within the MRI system or that are not integrated within the MRI system. Imaging coils integrated within the MRI system can be used for general investigations, for example, investigations of a large area of the patient's body. For an investigation of a particular body part, imaging coils external to the MRI system can be positioned near the body part. For example, if the patient's carotid artery is being investigated, the technician might be required to place an external HF coil adjacent the patient's carotid artery.
In Step S806, at least part of a patient's body is positioned in the MRI system.
In Step S808, the technician defines one or more recording sequences suitable for a particular diagnostic inquiry. Excitation and measurement signals transmitted and received by the HF and gradient coils during each MRI scan are based on parameters included in each recording sequence. Each recording sequence can include a plurality of parameters that can be changed by the technician via a user interface, which can be time consuming.
Multiple recording sequences can be used to obtain multiple properties of an object at various resolutions and degrees of contrast. Multiple recording sequences can be used to address differing requirements of different diagnostic inquiries.
In Step S810, a scout recording is obtained. The scout recording can be a general image of an entire object. The scout image can be used to check whether the patient is positioned properly with respect to the imaging coil. The scout image need not have an image quality that is sufficient for making a diagnosis. The scout recording can be required for defining the final region of interest during subsequent scans, which can be quite time consuming
In Step S812, a sensitivity profile of the imaging coil is generated based on a plurality of measurements. The sensitivity profile of the coil depends on the location of the coil within the magnet. If the location is fixed, the sensitivity profile remains the same. The sensitivity profile can be used to correct subsequently obtained diagnostic images. The sensitivity profile can be used in conjunction with parallel imaging techniques. If parallel imaging techniques are not used, the sensitivity profile of the imaging coil need not be generated.
In Step S814, a target volume is defined within a scout volume or three-dimensional region corresponding to the scout image obtained in Step S810. The target volume defines a three-dimensional region in which a diagnostic scan is to be performed to obtain a recording of a diagnostic image. An image quality of the diagnostic image is often greater than the image quality of the scout image.
It is noted that the sensitivity profile of the receive coil does need not necessarily be measured in a separate step before each image acquisition. If a scout image is taken, the scout image is a convolution of an MR signal of the object with a sensitivity profile of the receive coil. Measurement of the sensitivity profile of the receive coil can be integrated into the scout scan or even directly into an imaging sequence. For the latter method, no separate calibration step is needed. Generally, coil calibration procedures do not require user interaction.
In Step S816, one or more diagnostic images are recorded based on the imaging sequence(s) defined in Step S808. The process ends in Step S818.
In general, a highly-skilled technician is required to perform Step S804. Such a highly-skilled technician should have great expertise and precise knowledge of a target organ that is to be examined, in order to ensure that the imaging coil is optimally positioned relative to the area being examined. A highly-skilled technician also can be required to perform Step S808, as the technician should understand a correlation between a particular recording sequence and a particular MRI application, such as a dental MRI application, for example. Additionally, performing Step S808 can include entering parameters that define the recording sequence via a user interface, which can be time consuming. Thus, the amount of time needed to perform an examination that includes Steps S810 to S814 often can be long compared to examinations that do not require a scout image to be obtained.
Accordingly, it would be useful to provide an imaging system that enables an operator to quickly perform a diagnostic examination, without requiring the operator to spend time generating a recording sequence that is used by the imaging system to perform the diagnostic examination or for manual, interactive target volume definition. Additionally, it would be useful to provide an imaging system that can be operated by technicians who are not necessarily highly trained and/or skilled.